An air conditioning system is a closed system, which operates on pressure difference and change of state that the coolant gas is subjected to throughout the circuit. The components in question are:                the compressor suctions and compresses the coolant, modifying its state and the temperature (from low pressure and low temperature to high pressure and high temperature); it has the function of compressing the coolant gas, making it pass from low temperature and low pressure to high temperature and high pressure. It is a precision component, whose quality has a major impact in terms of safety, comfort and energy saving. The compressor contains rotary parts, and thus should be suitably lubricated with a specific oil, with characteristics suitable for the refrigerating circuit;        the condenser transfers heat to the external air and condenses the coolant, which thus passes from the gaseous state to the liquid state; in practice, it is a heat exchanger which serves to cool and thus liquefy the coolant gas coming from the compressor; it is mainly formed by ducts (primary exchange surface) and fins (secondary exchange surface). Usually, in vehicles it is positioned in the front part, before or beside the engine radiator. It transfers heat to the environment, given that its temperature is higher with respect to the one surrounding it. The air passes through the fin elements of the condenser and, by subtracting heat, it causes the liquefying of the refrigerating fluid or coolant;        the coolant traverses the de-hydrating filter, which absorbs moisture and withholds impurities (the de-hydrating filter is placed between the condenser and the expansion valve and it is traversed by coolant in high pressure liquid state); the coolant then reaches the expansion valve, where it is subjected to a drastic pressure and temperature drop;        in the evaporator, the coolant once again changes its state, passing from liquid to gaseous. It absorbs heat and lowers the temperature of the air introduced into the cabin through the aeration ducts; the evaporator is also a heat exchanger. It is conceptually identical to the condenser though having the opposite function. Inside, the coolant passes from the liquid state to the gaseous state absorbing heat from the environment. The air which traverses the fins thereof is cooled and enters into the cabin through the aeration ducts.        